B.J. Casey, Ph.D.
SUMMARY: Dr. B.J. Casey reviewed her model of cognitive control (executive function), as well as the behavioral and imaging studies that have examined the neural processes underlying its development. An essential component of executive function is the ability to predict when events will occur, which is critical for planning and maintaining appropriate thoughts and actions. When these expectations are violated, one must employ a form of detection that triggers adjustments in behavior (cognitive control) to override inappropriate thoughts and actions. This ability continues to develop throughout childhood, but is disrupted by a number of childhood disorders, including childhood-onset schizophrenia, attention deficit hyperactivity disorder (ADHD), and substance abuse.
Casey and her colleagues used fMRI and diffusion tensor brain imaging (DTI) to map connectivity of frontostriatal, frontoamygdala, and frontocerebellar neural circuits involved in the development of cognitive processing and control. Subjects completed a battery of tasks, which required inhibition of a stimulus, inhibition of a behavior, and complete inhibition of a response. Some tasks attempted to elicit appropriate responses after presentation of cognitive information that violates expectations. Images of activated brain areas were captured, then correlated with behavior.
Significant differences were noted between adults and children. Task accuracy increased and reaction time decreased on stimulus selection tasks as normally developing children approached puberty, and adult levels of accuracy were reached by adolescence. Schizophrenic subjects had difficulty suppressing irrelevant but salient stimuli during the stimulus selection tasks, while children with ADHD showed deficits on both the stimulus selection and response execution tasks. Lastly, adolescents demonstrated enhanced activation when presented with unexpected stimuli.